Elk City aquifer report

Water use and general info

The Elk City Aquifer underlies parts of Beckham, Custer, Roger Mills, and Washita Counties in western Oklahoma and covers 519 square miles. The mean annual water use was 2,314 acre ft from 1967-2018, corresponding to roughly 2.1 million gallons per day (Wagner et al. 2021).

Find or download well water levels

EPA-regulated contaminants

Primary Maximum Contaminant Levels

The EPA has established National Primary Drinking Water Regulations, called Maximum Contaminant Levels (MCL) to protect the public against consumption of drinking water contaminants that present a risk to human health. These are shown along with the aquifer statistics in Table 1 below:

Table 1: Aquifer statistics and EPA Primary MCL values. Green result values with down arrows indicate that aquifer median concentrations are below the MCL. Red values with up arrows indicate that aquifer median results are above the MCL. A “<” symbol indicates the result value is below the laboratory reporting limit. Median* = estimated aquifer-wide median using bootstrapping, a robust statistical method; μg/L = micrograms per liter (1 g/L = 1,000,000 μg/L); mg/L= milligrams per liter (1 g/L = 1,000 mg/L).

No median aquifer concentrations of EPA primary contaminants exceed their MCL’s, but some individual wells meet or exceed MCL’s for arsenic, cadmium, and nitrate/nitrite.

Secondary Maximum Contaminant Levels

The EPA has established non-mandatory National Secondary Drinking Water Regulations, called Secondary Maximum Contaminant Levels (SMCL), to assist public water systems in managing their drinking water for aesthetic considerations such as taste, color, and odor. These contaminants are NOT considered to present a risk to human health at the SMCL. The SMCLs and aquifer statistics are in Table 2 below:

Table 2: Analytical results and EPA Secondary SMCL values. Green result values with down arrows indicate results are below the SMCL. Red values with up arrows indicate results are above the SMCL. A “<” symbol indicates the result value is below the laboratory reporting limit.

No median aquifer concentrations of EPA secondary contaminants exceed their MCL’s, but some individual wells meet or exceed MCL’s for total dissolved solids (TDS) and mananese.

EPA Health Advisories

The EPA has issued additional health advisories for some parameters in drinking water. These health advisory values and the aquifer statistics are shown in Table 3 below:

Table 3: Analytical results and EPA Health Advisory values. Green result values with down arrows indicate median concentrations below the Health Advisory. Red values with up arrows indicate median concentrations that are above the Health Advisory. A “<” symbol indicates the result value is below the laboratory reporting limit.

Median sodium concentrations for the Elk City Aquifer exceed EPA health advisory concentrations. No other contaminants meet or exceed health advisory concentrations.

General Chemistry

Most samples in both 2013 and 2019 indicate a calcium magnesium bicarbonate water type, with almost equal amounts of calcium and magnesium.

Find or download geochemical data

Click the link below to download all water chemistry data for the Elk City aquifer.

Download aquifer chem data

You can also select results from the most recent sample for each individual site with the table below:

Wagner, D. L., Sanford, J.E., Sean, P.H., Spears, K.W. and Fiorentino, E.G. Hydrologic Investigation Report of the Elk City Sandstone Aquifer in West Oklahoma, 2019. OWRB. https://www.owrb.ok.gov/studies/pdf_stu/ElkCitySandstoneAquiferReport_20211221_DLW.pdf